libcruft-util/m4/nc_optimisation.m4

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AC_DEFUN([NC_OPTIMISATION],[
##-------------------------------------------------------------------------
AX_REQUIRE_DEFINED([AX_APPEND_COMPILE_FLAGS])
AX_REQUIRE_DEFINED([AC_CANONICAL_HOST])
AX_REQUIRE_DEFINED([AX_COMPILER_VENDOR])
AX_COMPILER_VENDOR
##-------------------------------------------------------------------------
## Enable LTO
AC_ARG_ENABLE([lto], [
AS_HELP_STRING([--enable-lto], [enable link-time optimisation])
])
AS_IF([test "x$enable_lto" == "xyes"], [
AS_IF([test x"${host_os}" == x"mingw32"], [
AC_ERROR([mingw32 link-time optimisation is currently broken])
])
AS_IF([test "x$ax_cv_cxx_compiler_vendor" == "xgnu"], [
AC_CHECK_TOOLS([RANLIB], [gcc-ranlib ranlib])
AC_CHECK_TOOLS([AR], [gcc-ar ar])
AC_CHECK_TOOLS([NM], [gcc-nm nm])
])
AX_APPEND_COMPILE_FLAGS([-flto], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-fno-fat-lto-objects], [], [-Werror])
AX_APPEND_LINK_FLAGS([-fuse-linker-plugin], [], [-Werror])
])
##-------------------------------------------------------------------------
## Choose the most performant processor architecture and features
AC_CANONICAL_HOST
AS_CASE([$host_cpu],
[x86_64], [
AX_APPEND_COMPILE_FLAGS([-mtune=generic], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-msse], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-msse2], [], [-Werror])
],
[i686], [
AX_APPEND_COMPILE_FLAGS([-march=prescott], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-mtune=generic], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-mcmov], [], [-Werror])
],
[AC_MSG_WARN([unknown host_cpu])]
)
AX_APPEND_COMPILE_FLAGS([-pipe])
AX_APPEND_COMPILE_FLAGS([-mfpmath=sse], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-msahf], [], [-Werror])
##-------------------------------------------------------------------------
## Enable aggressive code generation optimisations
AS_IF([test "x$enable_debugging" != "xyes"], [
AX_APPEND_COMPILE_FLAGS([-ftree-loop-distribute-patterns], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-ftree-loop-if-convert-stores], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-ftree-vectorize], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-funsafe-loop-optimizations], [], [-Werror])
# gcc >= 4.8 defaults to enabling stack-protector, we care more about
# performance than security.
AX_APPEND_COMPILE_FLAGS([-fno-stack-protector], [], [-Werror])
])
##-------------------------------------------------------------------------
## Enable code size optimisations (that don't impact performance)
## Note: we assume CXX, and that CXXLINK is g++ not ld, hence the -Wl opt
AS_IF([test "x$enable_debugging" != "xyes"], [
AX_CHECK_LINK_FLAG([-Wl,--gc-sections], [
AX_APPEND_COMPILE_FLAGS([-fdata-sections], [], [-Werror])
AX_APPEND_COMPILE_FLAGS([-ffunction-sections], [], [-Werror])
AX_APPEND_LINK_FLAGS([-Wl,--gc-sections], [], [-Werror])
])
])
])